This invention relates to barriers (hereafter "sound barriers") for use along highways, railroads, airports, and other transportation facilities, and industrial areas and the like, whether the barriers be mounted on the ground or on structures, and to acoustic panel assemblies useful in such barriers as well as in other constructions.
The need for sight, sound and security barriers in urban and industrial environments to control highway, railway and rapid transit sounds and sights is well recognize. In the past and presently, some barriers have been mere fences, often made of wood. In more recent times, increased urban densities, higher traffic spas and volumes, high percentages of loud truck traffic, and a heightened environmental awareness of the problem of noise has led to increased sophistication in the construction of sound barriers. A relatively common construction of a sound barrier now includes concrete or steel flanged posts mounted in or bolt to concrete foundations in the ground, or mount on parapets or bridges or other structures. Distances between posts range from approximately eight feet to twenty feet and more. Concrete, plastic or wood panels in lengths which span between the posts are stacked atop one another to desired heights, with panel ends slid between the post flanges. Constructions of this type have numerous advantages, including speed of erection, low cost, opportunity for disassembly, if necessary, and portability for reassembly at another location. These barriers typically provide some reduction of sound transmission through the wall materials, but are usually accompanied and burden by heavy material weights. Most of the materials reflect sound, which decreases barrier effectiveness in both single wall and parallel wall configurations where, for example, barriers on the opposite side of a highway reflect sound and create reverberating noise which decreases barrier effectiveness.
An advantageous advance in sound barriers has been the utilization of Durisol.TM. products in such barriers. Durisol.TM. products are available in the United States from The Reinforced Earth Company, Vienna, Va. Durisol.TM. products utilize Portland Cement and long, thin, specially treated wood shavings as the aggregate. The resulting wood concrete is hard, lightweight, porous, free draining to water, resistant to rapid and severe freezing and thawing cycles, even in the presence of road de-icing chemicals, resistant to attack by termites and vermin, has low smoke generation and flame spread characteristics, and has thermal insulating properties. Due to its porous nature, it is also sound absorptive. These qualities have made Durisol.TM. a product suited for use in many applications, including block wall forms, concrete forms, roof plank, and insulating cores for wall panels. The utilization of Durisol.TM. wood concrete products as construction materials predates the 1940's in Europe. Durisol.TM. products have also been made for over 30 years in Canada. Durisol.TM. products are presently manufactured in the Netherlands, Austria, Morocco, France, Spain, Italy, Hungary, Germany, Yugoslavia, Japan, Algeria, and the United States.
Durisol.TM. products have significant air voids, and the wood concrete construction is lighter than Portland cement concrete made with natural sand and aggregates. Sound barrier panels may be faced with Durisol.TM. material by layering Durisol.TM. material, concrete, and more Durisol.TM. material in panel molds. The resulting Durisol.TM. faced panels are durable but lightweight relative to other concrete panels. Durisol.TM. panels are also sound absorbent relative to other concrete panels. Effectiveness of sound barriers constructed with Durisol.TM. faced panels is improved from one to six additional decibels according to test reports. This is an improvement of ten to sixty percent relative to reflective walls which are designed, generally, to provide 10 decibels of noise reduction.